Note: Descriptions are shown in the official language in which they were submitted.
CA 02479571 2004-10-05
I) Title
Photodegxadation of Toxic Organic Contaminants
This application is a division of Canadian application
No. 2,127,242.
~~ 8ackcLround of the Invention
(i) Field of the Invention
This invention relates to the degradation of toxic
organic contaminants.
(ii) Background Axt
Toxic organic contaminants include polychlorinated
dibenzo-p-dioxins and polychlorinated dibenzofurans, which are
large groups of chloro-organic compounds tahioh have become
ubiquitous in industrial societies. Of the various possible
isomers of, these compounds, the following are reportedly
~.5 extremely toxzc a
2,3,7,8-tetrachloradibenso-p-dioxin, 1,2,3,7,8-
pentachlorodibenzo-p-dioxin, 2,3,7,8-tetrachloradibenzofuran,
1,2,3,7.8-pentachlorodibenzofuxan, 2,3,4,7,8=
pentachlorodibenzofuran, 1,2,3,5,7,8-'hexachloxodibenaa-p-
2o dioxin, 1,2,3,7,8,9-hexachloradibenza-p-dioxin, ~,,2,3,4,7,8-
hexachlarodibenzo-p-dioxin, 1,,2,3,6,7,8-
hexachlorodibenzofuran, 1,2,3,7,8,9-hexachlorodibenzafuran,
1,2,3,4,3,8-hexachlorodibenzofuran, and. 2,3,4,6,7,8-
hexachlorodibenzofuran.
25 Polychlorinated dibenzo-p-dioxins and polychlorinated
dibenzofurana are known to cause a temporary form of a skin
ailment known as P'chlor-acne". Also, polychlorinated dibenzo-
CA 02479571 2004-10-05
2
p-dioxins and polychlorinated dibenzafuxans (particular7.y
2 , 3 , 7, $-tetrachlorodiberlzo-p-da.oxin) have been found to be
extremely toxic to certairn animals in labdz~atory studies.
Because o~ this reported high level of toxicity in
laboratory tests, there is a general concern as to the long-
term effects of polychlorinated dibenzo-p-dioxins and
polychlorinated dibenzofurans an human physiology.
Accordingly, there is an importane need to remove or
substantially reduce the content of polychlorinated dibenzo-p-
a.0 dioxins and polychxorinated dibenzofurans from used telephone
poles, used railway ties, used fence posts, etc., prior to
disposal or reuse of the waste. There is also a need for a
process for treating solutions containing toxic organic
contaminants, as described above, and including toxic organic
~5 contaminants which have been removed from treated wood, so
that they can be disposed of safely.
Pentachlorophenol-treated utility poles contain high
levels of pentach~,orophen.ol and related contaminants, and
consequently can not be disposed of in landfill sites. zt has
20 been suggested to use bioremediation as a possible tnray of
decontaminating ~:he~se materials. Poles removed from sex-vice
have a high pentachlorophenol content, i.e., of the order of
about 5,000 - 27,000 ppm in the outer 20 mm zone, This high
~.evel of pentachlorophenol is toxic to most microorganisms
25 which have been suggested for use in the biaremediation
process. AcCOxdingly, it is necessary to pre-treat the pole
CA 02479571 2004-10-05
3
material Go reduce the content of such contaminants before
biological remedza~.ion,
physical or chemical methods can k~e used for the pre-
treatment process, Physical methods, e.g,, dilution, i.e.,
mixing the pentachlorophenol-containing sawdust with large
amounts of uncontaminated sawdust or other materials, so that
the pentachlorophenol concentration is low enough for the
microorgan~.sms tv survive, ins not feasible economically. zt
also has the problem of generating a much larger volume of
contaminated waste. Therefore, any kind of dilution approach
is not considered to be suitable.
Solvent extraction is probably tY~e easiest and most
effective laboratory method of removz~ng pe:ntachlorophenol from
contaminated wood. However, extraction using organic solvents
is also not cansidexed appropriate commercially, because of
env~.ronmental concerns and tha hazards involved in a large
scale operation.
Chemical treatment has also been, suggested for pre-
treating the pentachlorophenol-containing wood before
bioremediation. Pentachlorophenol is, however, very stable
and onl~r a few systems can modify and/or degrade this
molecule. $ecause of the strong, relatively non-polar
covalent C-C1 bonds in gentachlorophenol, removal. of the
chlorine by hydrolysis i$ difficult, Pentaahlnrophenol is an
2~ electron-deficient molecule and should be more reactive
towards reduction than ox~,da~ion. Potassium-graphite-
CA 02479571 2004-10-05
4
intercalate has been suggested as an agent for dechlorinatiorx
of a number of compounds inaxuding pentachlorophenal and
actachloradibenzo-p-d~,oxin. This systEm, however, requires
inert atmosphere, high temperature and absa7.ute anhydrous
aanditions and is impractical .for large kale applications.
Electraahemical reduction has been xauggested for use far
treating waste waters containing law ct~ncent~rations of
chlorinated arganics. Such process was considered not
suitable s~,nce, far electrochemical processes to work, the
1.0 electrodes must maintain clean surfaces. Moreover, the oil
and Qther contaminants iz~ pentachlorophenol-treated Wood would
contaminate the electrodes very quickly.
Reductive dechlari,nation of chlorinated organic compounds
by photochemical reactions has also been suggested to detoxify
pent,achlorophenol~cvntaining materials. Photochemical
degradation of pentachlorophenol and lower chlorophenals in
the presence, or absence, of rrarioua phatosensitizers az~d
catalysts have furthermore been suggested. 2t is known that
polychlorinated biphenyls may be dechlorirlated in the presence
z0 of visible dyes and amines using visible light.
Oxidation of chlorophenols by enzymes has also been
suggested. Laccases may be used tv remove chlarophenols from
water through polymeri2ation. This method, however, does not
provide a permanent solution to the problem. The oxidation
2~ of phenolic palzutaz~ts by lignin peroxidase, an enzyme from
PhatZerac~haete ch,rysosporium, haB also been suggested. On the
_.., _.,, . ~...~:,~,.~.,~ $~,.,~ .~ _ .__. __..__ ._ M ___.. _. ..
CA 02479571 2004-10-05
other hand, it is l~nown that chlorophenols could be converted
to much more toxic polychlorodibenao-p-dioxins by peroxidase
catalyzed oxidation.
Supercritical fluids have also been $uggegted to extract
5 ceZluZoaic materials, A supercritical fluid (8CF) is a fluid
at a temperatur°e above its critical value. ~.n SCF has
prvpert~.es which axe intermediate between these of gases and
liquids. It has a viscosity which is lower than that of a
liquid and a density which is higher i~hax~ that of a gays.
These properties allow SCFs to penetrate matrices easily,
while reta~,ning reasonable dissolving power. Supercritical
fluid extract~.on (an FE) is a technique in wh3.ch gases are
compressed under supercritical conditions to form a fluid,
' which is then used to remove chemicals from a matrix. Among
the various solvents suitable for SFB, carbon dioxide is the
most commonly used, because it is non toxic, non-flammable,
and zne~epensive. Carbon dioxide also has low critical.
temperature and pressure, thus having a minimum requirement
for equipment design, SFE provides superior extraction to
2o routine sal~crent extraction in several aspects. For example,
SFE lea~crc~s no solvent residue in the matxisc after extraction,
since carbon dioxide is a gas at normal temperature and
pressure. The extract is automatically separated from the
$ohrent when the pressure i;s released (carbon dioxide under
rtvn-Critical conditions can hardly dissolve any of the
extracty, and since it eliminates Che solvent-extract
CA 02479571 2005-12-23
6
separation step, it is very energy efficient. In addition,
SFS can be done in a closed system where carbon dioxide i$
continuously recycled.
A discussion of background art relating to SFE is
included in my co-pending Canadian patent application No.
2,127,242, to which the reader is directed far reference,
It is thought that the degradation of pentachlorophenol,
polychlorinated dibenzo~p-dioxins and polychlorinated
dibenzofurans in solution and in sawdust slurry may be
achieved by photochemxcals reactions. However, a
commercially-viable photochemical degradation process has not
been taught by the prior art.
An object of this invention is to provide a commercially
viable process for the degradation of such extracted
contaminants.
3 ) Summary of the Inyention
fi) Statement of Invention
According to a first aspect of the invention, there is
provided a process for photodegrading organic toxic chemicals
which process comprises the steps of:
providing a solution of said organic toxic chemicals, a
solvent and a photosensitizing amount of a photosensitizes
which is selected from the group consisting of a porphxrzn and
a phthalocyanine; and
exposing said solution to radiation which is selected
from the group consisting of w and sunlight.
(ii) other Features of the Tnvention
Preferably, the radiation comprises direct sunlight.
'Ihe sol~rent may be selected from the group consisting of
acetonitrile, methanol, ethanol, and other water-miscible
solvents.
CA 02479571 2005-12-23
7
~n embodiments of the invention, the process may take
place in the presence of an amine, e.g., triethanolarnine.
5 2n embodiments of the invention, the photodegradation to
~~wYfl~a H~~ ~~v:~ ~r~~r:~ ~~~~~~;r~rtc
CA 02479571 2004-10-05
may take place i.n a slurry of wood caz5taminated with said
contaminants, or the gh4t.odegradation to degrade toxic organic
chemicals may take place in a liqu~.d solvent phase.
~) nescription c~f Preferred F~nbodiments
Photodegxadation processes embodying the present
invention may b~: employed after first e~ttracting the organic
to~sic eontami,nants using a supercritical fluid extraction
tSFE) disclosed and claimed in copending Canadian patent.
~fl app~.ication No. 2,127,42 to which the reader is directed far
details.
~~,ICALS USED
All the chlorophenol and dihydroxychlorobenzene standards
z5 were obtained from Fluka. PentachlorophenaX wa.s 99% pure from
Aldrich and was used without further purification. Tecrsnical
grade pentachloraphenol, manufactured by KMG, was provided by
a presexwatxve treating plant. Methylene blue double zinc
salt, was acquired from Mathesoxi, Coleman and dell.
20 Fhthalocyaninetetrasulfanate sodium salt was purchased from
Porphyrin Products. Protoporphyrin I~ was a gift from
Professor David Dolphin, Department of Chemistry, UHC.
Triethanolarnine (99.8%, certified) was purchased from Fishex-
Scienta,fic. All solvents were spectral grade (4ML~IISOT,vz,",)
25 from BDH and all other chemicals were of analytical grade.
CA 02479571 2004-10-05
GENERAL PROCEDURE
EbUIPMEN'T USED
a The GCMS was a VG Trio-1000 system equipped with a 3 Q
meter DB-5 column. The reagent gas for chem~.cal ionization
(CI) QCMS was ultra high purity methane. GG-ECD (electron-
capture detector.) was carried out on a ~-~p 5890 II GC with a
30 meter DS-1 column. sample injection for the GC-ECD was
20 done by using a HP ~67o autosampler.
Several examples will be described to illustrate
photodegradation of organic toxic compounds in accordance with
this invention. In each Case, the compounds are placed in
solution with a suitable phvtosensiti2ex~.
EXAMPLE 2- Photochemical bec~radaCion of Pentachlorophenol
The photochemical degradation of pentachlorophe~aol waa
first studied using 1:1 acetonitrile/water (volume) as the
Rfl~ VI~51'~ Ta~'1~ d 1 ~'1r-~~ A~.Y c~nc.Ta 1~~1W raoml i-t.
CA 02479571 2004-10-05
xo
TABLE 1
Photochemical Dag~radation of Pentachlorophenol (2xlb'3 M? in
1:1 Acetonitrile/Water (volume) in the Presence of
Triethanalamine (0.02 M) and Various Sensiti~ers (1x10'3 M)
Ph4tosensitizer POTS Mix* Methylene Protoporphyrin
Blue IX
lb
Time (hours) PCP Con,~ent ratxor~ (fpm)
0 500 500 500 500
1 165 91.6 43.2 20
2 71.6 28 1.2 2
3 36 1.6 0 b
24
4 15 0 a 0
5 8 0 0 0
6 3.2 0 0 0
7 1.5 0 0 0
* : A mixture of PCTS (ghthalocyaninatetrasulfanatey
, m~ethylene
blue, arid protopoxphyri.n IX, each at x ~0"4 M
3.33
As can be seen from Table Z, pentachlorophenol
wag
rapidly degraded. only pentachlorophenoland trace amounts
of tetrachldropheno7a were detested by GCMS after acetic
anhydride derivatization. Protopoxphyrin
IX was the mast
effective photasensitiaer, with methyleneblue only slightly
less effective. Over 99~ of the pentachlorophenol
was
destroyed within two hours using either metklylene blue or
protoporphyrin IX as sensitizers.
CA 02479571 2004-10-05
1Z
The reaction was then repeated in 50~ (volume)
aqueous ethanol which was cheaper and less toxic than aqueous
acetonitrile.
Table 2 shows the results of such photochemical
degradation.
T~BLF~ 2
photochemical degradation of Pentachlorophenol (2x10'' M) in
1:1 Acetonitrile/Watex (~crolume) in the Presence of
Triethanolamine {0.02 M) arid various Sensitizers (1x10-9 1~)
~. 0
Photosensitizes POTS Methylene Prc~toporphyrin
Blue IX
Time (minutes) PCP Concen tration (npm)
0 500 500 500
3d 229.5 17.0 ~?
60 190 5.5 1.5
90 139 0.25 0
120 103 0 0
150 75.5 0 0
180 46 0 0
As can be seen from Table 2, the photochemical
destruction of pentachlorophenol in this solvent was fast.
within just ~. hour, over 99~ of the pentachlorophenol was
degraded. Protopox~phyrin was again the most effective
sensitizes. The differences in the efficiencies of the three
CA 02479571 2004-10-05
1~
sensitizexs was probably due to thezr different extinction
coefficients as shown below in Table 3.
TAHL~ 3
Extinction Coefficient of ~k~ree dyes in 1:1
Ethanol/Water (volume)
rye Absorption Maxima (nm) Extinction
Coefficient (M'lcm'~j
Methy~.ene
slue X60 5.8 x ZO°
25 Phthaloeyanine-
tetrasulfonate E37 4.0 x 104
3,99 x 10'
20 Proeoporphyrin
2X 378 1.48 x 10~
25 Protoporphyrin has an extinction coefficient almost four
times larger than that of phthalocyaninet:etrasulfanate in 54~s
ethanol. All three sensitizers absorb light at different
wavelengths. ~t was thought that if the three sensitiaers
were mixed tdc~ether, they would absorb light efficiently over
3a a wider range of wavelength and therefore would be more
efficient in degrading pentachlorophenol than any individual
sensitizers. As can be seen from Table Z, the mixture system
containing three sensitizers, each at one third of their
regular concentrations, was more effective than
35 phthalocyaninetetrasulfonate, but still ~.ess effective than
protoporphyrin TX or methylene blue, While it is not desired
to be bound by theory, ~.t is believed that this was probably
CA 02479571 2004-10-05
13
due to the low extinction coefficient of
phthalooyaninetetrasulfanate,
The formation of by-products from the photochemical
degradation of pentach7.orophenol was caz~efully studied by GCMS
analysis of a concentrated extract derivatized with.
diazomethane. Szx products including 2,3,~,6-
tetrachZorophenol, tetrachlorohydroquinone,
tetrachsoracatechol, tetrachlaroresorainal, and dichZoromaleic
acid were detected, These are shown beT_ow.
1~
oh " off
cy, cl of o cr w
'CI A 'GI CI ~ ~CI
CI
rl d
1~
1 ~ cl I
a h xHe
CI Ci CI q tr OOyN
i
cl ~ ''orl a ~ 'a d
of
20 AZ1 these groduets were present only in trace amounts as
shown below in Table 4. The identities of these product$ were
confirmed by their mass spectra, and by co~paring their ~C
retention times with those of sGandarde on two different
columns (DB-1 and DB-5)
CA 02479571 2004-10-05
a
O ~ r O O in ~ .~., w
o O o O C; ~ O o
v o a o o ~ c c c o
r
o r~ o 0 o e~s ~ ~ c~ o
°o, ~ ~ c'~.~ ° ~ rev, ~ e'~y, o '~
N O ~-~ C C7 O O ~.-~ G ~ G ~
0 o°,oMr~c~~~ L'~~~n,~e
r~ Sri o o ~ ,~., o
y
o ~ N '~ ' ~ o
o 0 0 ~ ~ a o
p, ~ef ° O O o C7 Q D O P
C ~.i
~D tP1 Y'f N ~ l'~ ~_ d
O Q O O C~ C O O C?
en O C C C ,7,., O ~ e~ D O d
G~i
h.
OOm.~O, ~.-~aN.~..G C
N c?~DCC? ,OOCi00
__ .. .
o ~ ~ w ~ ~ ~ ~ o
o ~ a c o o a Q o 0 0 ~
U
--. re o.,
c ~ U ~ U x ~ ~3 U O' sx f-~
0 0 ° 'M a V U ~ '~ a C~ U o
C. ~ F-~ F~ H E~ k~ E~ F~ E
m
a° .~ ... '°~ ~_
a ~a_9 "~s o
~~ '~0~0 ~ ~C
E~ ~-.1 C/7 b'~J
CA 02479571 2004-10-05
Z~J
It was also determined that photochemical degradation of
pentachlorophenol under sunlight, through a regular w~.ndow
glass filter, a7.lowed t~h,e accumulation of
zntermediatesJproduuts in some cases. In additic~z~ to the
products identified prev~.ous3.y, all three zsomers of
tetrachlorophenolB, six isomers of tr:ichlorophez~ols, 3,~- .
dichloraphenol, 2,~-dichlorophenol (and/ox 2,S~dichlorophenol,
2,4- and 2,5,dichlc~rophenols have the same retention time on
GC arid could not be distinguxshed7 , a dichlorodihydrt~xybenzene
~.0 and a trichlorodihydroxybenzene were detected, as shown below
according to the fo:~lowing scheme.
H H YI
~ CI
a .
°' °~ (a21 ,aix ieamera)
(andlor a.s-nC~>
.- ~ (aft). '
a o
ch
oy
(a11 three isomers7.
~ H ~H OH
ZL
Q ~ O' d G n . 0H P COOH
( _
r. cv d cooH
on i ~ .
The dichlorodihydrox~rbenzene and the
tx~ichlorodzhydroxybenzene were identified only based on their
2~ mass spectra, as no standards were available. All other
products were positively identified by comparing their mass
spectra and their retention times with those of standards on
CA 02479571 2004-10-05
16
two different G~ columns (DB-1 and DB-5). The
tetrachlorophenols and tetrachlorohydror~uinQne,
tetrachlorocatechol, arid tetrach3.ororesoreinol were present
in much larger quantities under filtered sunlight than those
of the reaction under direct sunlight.
photodegradation of pentachlorophenol in a slurry of
pentachlorophenol-containing sawdust in water was also studied
uszng protQporphyrin I~ and methylene blue as sen$itizers.
The results are summarized in Table 5 below.
TAHLE 5
photochemical treatment of sawdust (1 g~, 27,0100 ppm FCp) in
mL 1:1 ethanol/water (volume) in the presence of a
sensitizer (l~lOw M) and triethanolarnine (0.02 M)
15 _
PCP Concentration (ppm)
Methylene Hlue Protoporphyrin
20 La.guid Phase Sawdust Liquid Phase Sawdust
Timethrs)
0 540 27,000 6&7 27,000
~5 (l, 500 (l, 500)
W
1 897 -- 536 T-
2 702 -~ 237
3 170 -- 107 ~ --
4 53.5 948 23.2 791
(5I7) f161)
5 12.'7 -- g.3 __
6 6.0 -- 4.7 __
7 5.5 -- 6.1 __
8 4.I 145 4.4 115
(0) (0)
*: Data in brackets concentratianof 2,3,4,6-
tags the
tetrachlorophenol
in ppm
CA 02479571 2004-10-05
i~
As can be seen from Table S, pentachlorophenol
concentration in both. liquid and solid phase decrease rapid~.y.
lifter eight hours' of irradiation,, only 4 ppm of
pentaChlvraphenol remained in the liquid phase, and 115-145
ppm of pentachlorophenol remained in the solid phase.
EXAMPLE 2- PhotodeQradation of Dioxins and ~uran5
The change ix~ the concentration of polychlorinated
lp dibenao-p-dioxins and polychlorinated dibenzofurans due to
photochemical degradation of pentachlorophenol eras
i ryvczsz~ i araf pry T~ho rr~aml t-Q err nx,r,n~n 'hAl r,s.r v r~ T~i,l a ~
CA 02479571 2004-10-05
z'.
4
~H
0
~ d M G ~ O
,.
M
O O
ro ~ ~ a
V ~ °M°
0
. '~ ~ D . _
V
ro
U ~ ~y~o~~s°a
° ~ ~'~ ~"~ ~"~
o v°c ,~ ~y, a.
V .°c ~' M oa o
'o ~ ~ ~ ° a
w ~ ~d ~ ~ ~ oNO ~ '$ a~ .o
~y ».. .fl
°'
°~.~'~~°
~'~,~~ ~~,~.~ ~
c: ~ ~ ~" at ,.., x
U,~° w°~s.oaa~'a °o.Q
o y ~~ A ~ II ~~ u, W
~ ~ ~ N q 0~., (,~~C,4")q~~~V 0.,~
V ~ r~ et N L~i 5Y q,a «~1 ~ ~ P., O ~r
v~
'_~
.
A
o x x o
CA 02479571 2004-10-05
19
z~ can bP seen from Table 6 that the levels of
polychlorinated ciibenzo-p-dioxin$ and polychlorinated
dibenzofurans decreased in technical pentach~,oraphenal
dramatically after photochemical oxa.dation, with
octachlaradibenzo-p-dioxin reduced by over 70~. After
photochemical oxidation of pure pentachlorophenol, the levels
of octachlorodibenzo-p-dioxin also decreased as shown in Table
6.
Photochemical treatment of toxic wastes is attractive,
ZO in that it uses a free energy source, sunlight. A
disadvantage of this pxocess is that the reartians are ofter~
slow, because only a few contaminants can strongly absorb
sunlight. L~entaehworophenol has a wea7c absorption peak at
around 33p nm, which is a~ the high energy end of sunlight
spectrum and is degraded slowly. The use of photosensitiaers
and amines has been proved successful . Death pentachloraphenol
and polychlorinated dibenzo-p-dioxin/palychlorinated
dibenzofuran contaminants are degraded rapidly without the
formation of more toxic or more recalcitrant by-products . The:
trace amounts of products/intermed3,ates axe more easily
mineralized chemically ar biologically th;~n pentachloraphenal.
Dichlaromaleic acid, tetrachlorocatechQ7,,
tetrachlororesorcinol, tetrachloraquinone, and lower
chloraphenols have been identified a.s pentachlorophenol
photodegradation prad.ucts. Tetrachlorohydroquinone was a~.so
detected. The formation of a number of dimeric and trimeric
CA 02479571 2004-10-05
products during photodegradation of aqueous sodium
pentachlorophenate solutions have previously been reported by
others. However, no such compounds were formed under the
reactions descx~.bed above. In the present examples, it was
found that the presence of phr~tosensitizers and
triethanolamine did not result in an increase in
polychlorinated dibenzo-p-diox~.n/polychlorinated dibenzofuran
concentration. While it is not desired to be limited by
theory, it is thought that this was probably because
polychlorinated dibenao,p-dioxins arid pol.ychloradibenzofurara.s
were degraded at a rate faster than their formation. f~hile
it is not desired to be limited by theory, it is thought that
the photasensitizers and triethanolamine apparently xemained
unchanged after the photochem~,cal reaction. As a result, when
pentachlorophenol-containing sawdust is treated as a slurry,
the majority of the sensitizer az~d triethanolamine remains in
the liquid phase and thus can be reused.
It was previously found that in the use of solar
irradiation for treating soil. contaminated with wood
preser~rative wastes in solid phase, both pentachlarophenol and
polycyclic aromatic hydrocarbons were degraded. Th,e presenoe
of anthracene, a polycyclic aromatic hydrocarbon component of
the oil, enhanced the degradation of other coxttponents.
CA 02479571 2004-10-05
21
Operation of Preferred Embodime ~s
tn embodimezlts of the invention, photodegradation rnay be
used to degrade toxic organic chemicals from saZutions
thereof, regardless of the source of the contaminanted
solutions. Based upon current knowledge, bioremediation alane
is not expected to be able to detoxify all the polycyclic
aromatic hydrocarbons, pqlyck~lorinated dibenzo-p-dioxins and
polychlorinated dibenzofurans from treated poles.
Substantially-complete decox~.tamination of pentachlorophenol-
treated poles, by SfE treatment followed by photodegradation
can be achieved by using techniques as described in the
present application.
Thus, embodiments of this invention provide a process for
the photodegradatian of contaminants, especially following
e~ctractiøn from wood by the SfE process.
Moreover, embod~.ntenta of this invention provide a process
for the photodegradation of chlorinated oxganics without
separation from the eontamiz~ated material.
6? Conclusion
From the foregoing description, one skilled in the art
can easily ascertain the essential characteristics of this
ixa~rentiow, and without departing from the spirit and scope
thereof, can make ~rarious changes and modifications of the
invention to adapt it to various usages and conditians.
Consequently, such changes and modifications are properly,
CA 02479571 2004-10-05
22
equitably, and ~'inte~ded" to ba, within the full range of
equivalence of the following claims.
